Hello,
I'm having a similar problem whith user account and I dont have solution. The problem occurs when send email, the user works only from webmail. I try reindexing mail account but isn't solution. The error is:

Code:

method: [unknown]
msg: no such contact: 183102
code: mail.NO_SUCH_CONTACT
detail: soap:Sender
trace: com.zimbra.cs.mailbox.MailServiceException$NoSuchItemException: no such contact: 183102 ExceptionId:btpool0-36537://server.host.com/service/soap/SaveDraftRequest:1308590583692:baaf998428ede8ce Code:mail.NO_SUCH_CONTACT ArgitemId, IID, "183102") at com.zimbra.cs.mailbox.MailServiceException.NO_SUCH_CONTACT(MailServiceException.java:176) at com.zimbra.cs.mailbox.MailItem.noSuchItem(MailItem.java:1312) at com.zimbra.cs.db.DbMailItem.getById(DbMailItem.java:2281) at com.zimbra.cs.mailbox.MailItem.getById(MailItem.java:1251) at com.zimbra.cs.mailbox.MailItem.getById(MailItem.java:1247) at com.zimbra.cs.mailbox.Mailbox.getItemById(Mailbox.java:2083) at com.zimbra.cs.mailbox.Mailbox.getItemById(Mailbox.java:2054) at com.zimbra.cs.mailbox.Mailbox.getItemById(Mailbox.java:2045) at com.zimbra.cs.mailbox.Mailbox.getContactById(Mailbox.java:3173) at com.zimbra.cs.service.mail.ParseMimeMessage.attachContact(ParseMimeMessage.java:707) at com.zimbra.cs.service.mail.ParseMimeMessage.handleAttachments(ParseMimeMessage.java:481) at com.zimbra.cs.service.mail.ParseMimeMessage.parseMimeMsgSoap(ParseMimeMessage.java:368) at com.zimbra.cs.service.mail.ParseMimeMessage.parseMimeMsgSoap(ParseMimeMessage.java:204) at com.zimbra.cs.service.mail.SaveDraft.handle(SaveDraft.java:96) at com.zimbra.soap.SoapEngine.dispatchRequest(SoapEngine.java:401) at com.zimbra.soap.SoapEngine.dispatch(SoapEngine.java:276) at com.zimbra.soap.SoapEngine.dispatch(SoapEngine.java:157) at com.zimbra.soap.SoapServlet.doWork(SoapServlet.java:294) at com.zimbra.soap.SoapServlet.doPost(SoapServlet.java:215) at javax.servlet.http.HttpServlet.service(HttpServlet.java:727) at com.zimbra.cs.servlet.ZimbraServlet.service(ZimbraServlet.java:208) at javax.servlet.http.HttpServlet.service(HttpServlet.java:820) at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511) at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166) at com.zimbra.cs.servlet.SetHeaderFilter.doFilter(SetHeaderFilter.java:79) at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157) at org.mortbay.servlet.UserAgentFilter.doFilter(UserAgentFilter.java:81) at org.mortbay.servlet.GzipFilter.doFilter(GzipFilter.java:132) at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157) at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388) at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:218) at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182) at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765) at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:422) at org.mortbay.jetty.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:230) at org.mortbay.jetty.handler.HandlerCollection.handle(HandlerCollection.java:114) at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152) at org.mortbay.jetty.handler.rewrite.RewriteHandler.handle(RewriteHandler.java:230) at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152) at org.mortbay.jetty.handler.DebugHandler.handle(DebugHandler.java:77) at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152) at org.mortbay.jetty.Server.handle(Server.java:326) at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:543) at org.mortbay.jetty.HttpConnection$RequestHandler.content(HttpConnection.java:946) at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:756) at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:212) at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:405) at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:410) at org.mortbay.thread.BoundedThreadPool$PoolThread.run(BoundedThreadPool.java:451)